Thank you Heikki for your answer!
I can write a paragraph, (hence I did never do that => where can I find
info to contribute on the doc?)
But so far it's not quite clear to me:
You write "That really shouldn't be necessary", when I write that we have
to ship different drivers for each major PostgreSQL version...
Is this what I should document? Based on assumptions?
Further: Today we use a simple naming convention:
dbmpgs83x => for PostgreSQL 8.3.x
dbmpgs84x => for PostgreSQL 8.4.x
dbmpgs90x => for PostgreSQL 9.0.x
dbmpgs91x => for PostgreSQL 9.1.x
dbmpgs92x => for PostgreSQL 9.2.x
While we need to ship 5 drivers, this is clear and simple to understand.
If a future major version (for ex 9.3) implements a new strategic feature
that makes libpq headers incompatible with prior versions, what shall we
do with our convention? Shall we ship 9.x (where 0<=x<=2) drivers and 9.3+
drivers? What if a next major version implements again another feature
that makes headers incompatible again?
I think I am asking for is an official statement that clearly says that
libpq headers are only compatible for a given set of minor versions, like
(8.4.1, 8.4.2, 8.4.3, ...) or (9.2.1, 9.2.2, ...)
I believe also that the libpq library should automatically check for
compatiblity, based on PG_MAJORVERSION definition in pg_config.h ...
Seb
On 09/13/2012 09:01 AM, Heikki Linnakangas wrote:
On 12.09.2012 18:21, Sebastien FLAESCH wrote:
I believe there is some info missing in the page describing libpq
programs build:
http://www.postgresql.org/docs/9.2/interactive/libpq-build.html
I am working with PostgreSQL for several years now (since V7),
maintaining a set
of "db drivers" for our system, that can be used with the different
PostgreSQL
versions.
We need to build our binaries for different versions of PostgreSQL,
today it's
from 8.3 to 9.2 ...
What is the compatibility rule regarding this?
Can I compile / link with a PostgreSQL 9.1 environment and deploy on 9.2
???
Can I compile / link with a PostgreSQL 8.x environment and deploy on 9.x
???
If your binary is just a client application that uses libpq to speak to
the server, you can use any (supported) version of libpq with any
(supported) server version. There hasn't been any incompatible protocol
changes since version 7.4, which introduced the protocol version 3, and
even that was done in a backwards-compatible fashion so that even 9.2
server still supports the old version 2 of the protocol.
Now, another question is what happens if you compile your binaries
against e.g 9.1 version of libpq, but at runtime, you have 9.2 libpq
installed. I think that should work too, but not vice versa, if you use
any new functions from the 9.2 libpq library. In general, you should
have the same or higher version of libpq at runtime that the binaries
were built with.
The version number bump from 8.x to 9.0 was made because 9.0 introduced
many new features, but from a compatibility policy point-of-view, 8.4 ->
9.0 is no different than, say, going from 8.3 to 8.4.
The problem is that we have to ship several versions of the drivers
for all
the PostgreSQL versions that are in the support live cycle, today this is
from 8.3 to 9.2 ...
That really shouldn't be necessary.
So far, we followed the version policy as described here:
http://www.postgresql.org/support/versioning
I think it's ok to follow this rule, but would feel much better if it was
clearly stated in the "Building libpq Programs" page.
Agreed. Either that page, or the libpq top page at
http://www.postgresql.org/docs/devel/static/libpq.html, or a new
"cross-version compatibility" section under that. Could you write up a
few paragraphs for the manual please? That would be much appreciated,
you'd be in a good position to do that since you're facing the problem
right now.
- Heikki
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